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Abstract

Dual Process Theory provides a useful working model of decision-making. It broadly divides decision-making into intuitive (System 1) and analytical (System 2) processes. System 1 is especially dependent on contextual cues. There appears to be a universal human tendency to contextualize information, mostly in an effort to imbue meaning but also, perhaps, to conserve cognitive energy. Most decision errors occur in System 1, and this has two major implications. The first is that insufficient account may have been taken out of context when the original decision was made. Secondly, in trying to learn from decision failures, we need the highest fidelity of context reconstruction as possible.

It should be appreciated that learning from past events is inevitably an imperfect process. Retrospective investigations, such as root-cause analysis, critical incident review, morbidity and mortality rounds and legal investigations, all suffer the limitation that they cannot faithfully reconstruct the context in which decisions were made and from which actions followed.
In the National Post in 2008, columnist John Moore related
details of a murder: "a man fatally shot his wife in the chest and
got away with it." Our reaction is an immediate sense of outrage at
the ills of modern society. This is yet another example of wanton
domestic violence and of a judicial system that has failed, once
again, to bring the perpetrator of a horrifying crime to task -
"bleeding heart liberal judges and their hugs for thugs."

We later learn that the accused was an elderly man diagnosed
with a terminal illness, married for many years to a woman who had
developed Alzheimer's disease. He was fearful she would suffer
unduly without his care. Knowing, too, that his own death was
imminent, he chose to end her life. He was never charged with the
murder and was released home to await his own death, at least
content in the knowledge that his wife would not endure prolonged
neglect and suffering. The context, says Moore, removes our
outrage; we now understand both the husband's and the judge's
decisions (Moore 2008, April 7). After learning this, we might then
wonder, on reflection, "How could I have been so stupid to have
made the first judgment?"

We make decisions continuously throughout our waking lives.
These decisions vary in complexity from the simple, automatic
processes involved in executing a well-rehearsed habit, such as
driving a car, through more consequential decisions, such as
choosing a partner or deciding on a career. Decision-making is the
most important thing we do; it is the engine of all human
behaviour. In fact, how we live our lives derives from how we make
decisions (Gigerenzer et al. 2002). Yet, it is only recently that a
consensus has emerged about how the overall process of
decision-making occurs; this consensus appears to explain the
different ways in which we make decisions, as well as the
conditions and constraints that prevail.

Context

One of the major constraints on decision-making is context, as
described in the homicide example given above. It is graphically
illustrated in Figure 1. In the top line, the middle symbol is
clearly read as the letter B, whereas in the lower line, the
identical symbol is read as the number 13. A second example
is given in Figure 2, where two vertical bars are perceived to be
of different lengths because they are placed in the context of
perspective lines. The right bar appears to be extending both
higher and lower than the left line, thus appearing longer; but
both lines are the same length.

Many other visual illusions depend, for their effect, on
misleading context. Figure 3 shows the impact of juxtaposition on
the perception of size. The two white circles are the same size,
but the one on the left appears to be smaller.

Figure 4 shows the impact of contrast on the perception of
shading. The circles in each of the squares are actually the same
shade. The effect of contrast does not apply just to the shading in
illustrations - these contrast effects of context on
decision-making processes have been noted in the psychology
literature (Tversky and Simonson 2000).

Signal-to-Noise Ratio

Another way of looking at the issue of context is by applying
signal detection theory, so that we treat context as "noise." To
accurately perceive things around us, we need to be able to
distinguish critical signals from background noise (Swets et al.
1961). Few signals arrive in complete isolation; they are usually
accompanied by some degree of noise or interference. In each of
Figures 2, 3 and 4, our perception of the critical signal is
influenced by the surrounding visual noise. Similarly in medicine,
a particular problem for physicians is the degree of overlap among
diseases. Pathognomonic conditions (e.g., shingles, basal skull
fracture or shoulder dislocation; shown as A in Figure 5)
usually present little challenge for diagnosis; they are relatively
unambiguous and readily identified. They are accompanied by very
little noise. Other diseases (e.g., pericarditis and acute
myocardial infarction; B in Figure 5) manifest themselves
less clearly and may be mimicked by other conditions. Worse still,
some conditions (e.g., ureteral colic and dissecting abdominal
aneurysm, or subarachnoid hemorrhage and migraine; C in
Figure 5) may show complete overlap in their symptomatic
presentation. With these latter examples, the probability of
diagnosing the disease on the basis of clinical presentation may be
no better than chance; noise may completely overlap the signal.

In medicine, generally, there are many examples other than
disease mimics of distraction by noise. The decision-making of care
providers may be influenced by distracting cues (noise) from the
patient in front of them. Care providers may be influenced by
factors that may be irrelevant to the provision of appropriate
care, such as gender (Borkhoff et al. 2008; Hamberg 2004), race
(Green et al. 2007; van Ryn 2002), obesity (Hebl and Xu 2001; Hoppe
and Ogden 1997), psychiatric illness (Daumit et al. 2006; Mukherjee
et al. 2002) and age (Alliance for Aging Research 2003; Podolsky
and Silberner 1993).

Dual Process Theory

The dominant universal model of decision-making is Dual Process
Theory, which has attracted converging lines of support from
philosophical (Epstein 1994; Henden 2004), psychological (Evans
2008), neuroanatomical (Lieberman et al. 2004), neurophysiological
(Buschman and Miller 2007) and genetic (Oades et al. 2008) studies
and has recently been reviewed by Evans (2008). In Dual Process
Theory, there are two major decision-making modes: System 1 and
System 2. The processes of System 1 are intuitive, automatic, fast,
frugal and effortless. Examples of System 1 at work include our
initial reaction to the homicide described by Moore, and our
interpretation of Figures 1-4. In System one, contextual cues are
very important.

System 1's application to problem solving is nicely illustrated
by the Cognitive Response Test described by Frederick (2005). This
test consists of three questions:

A bat and a ball cost $1.10 in total. The bat costs $1.00 more
than the ball. How much does the ball cost?

If it takes five machines five minutes to make five widgets,
how long would it take 100 machines to make 100 widgets?

In a lake, there is a patch of lily pads. Every day, the patch
doubles in size. If it takes 48 days for the patch to cover the
entire lake, how long would it take for the patch to cover half the
lake?

The majority of answers given by respondents are wrong. For
question one, the usual answer is that the bat costs $1.00 and the
ball costs 10˘. This fast, intuitive response is incorrect because
the bat would then cost only 90˘ more than the ball. (The correct
answer is that the ball costs $.05 and the bat costs $1.05.) For
question two, the usual intuitive answer is 100 minutes, but again
this is wrong. One machine makes a widget in five minutes;
therefore, 100 machines would still take only five minutes to make
100 widgets. For question three, the usual answer is 24 days,
whereas the correct answer is 47 days. In each case, the answer
looks easy and intuitively plausible, but a moment's reflection
reveals that the first impulsive answer is wrong. Higher
mathematical skills are not required to calculate the correct
answer. These predictable errors can be explained, in part, by the
brain's "cognitive miser" function. This is an important but often
overlooked property of the brain - the tendency to limit cognitive
effort in reasoning (Krueger and Funder 2004), a kind of "energy
saving."

In contrast, the reasoning and decision-making processes of
System 2 are analytical, deliberate, slower, costly and effortful.
They are characterized, for example, by the reasoning processes
that allow the precise categorization, staging and location of a
brain tumour through neurological assessment, brain biopsy and
magnetic resonance imaging. A summary of the properties of the two
systems is given in Table 1.

Interaction between the Systems

There are several important ways in which the two systems
interact with each other, as is indicated by the broken lines in
Figure 6 (Croskerry 2009). Firstly, repeated presentations of the
same problem to System 2 can eventually result in the decision mode
being relegated to a System 1 level. This shows the benefits of
familiarity and practice - and the consequent development of
automaticity. Secondly, System 2 can exert an executive function
and override the impulsive output of System 1, the equivalent of
"turning off one's hot buttons." In the Cognitive Response Test
examples given above, a System 2 override takes no more than a few
seconds to run a mathematical check on the reflexive response.
Generally, this override function serves us well as taking
immediate action on first impressions can prove catastrophic.
However, System 1 responses can often be quite appropriate and best
left alone. In fact, too much scrutiny can result in "paralysis by
analysis." A good example of this is the memorable scene from the
musical, Oliver! in which Fagin repeatedly finds System 1
ideas appealing but each time rejects them by "reviewing the
situation." This System 2 override eventually incapacitates him,
and he ends up doing nothing.

Finally, and for the most part regrettably, System 1 can
override System 2. Often, this amounts to an irrational act, what
Stanovich (1993) has termed dysrationalia, a condition that
resonates with the ancient Greek akrasia: lacking command
over oneself, or the state of acting against one's better judgment
(Rorty 1980). There are a variety of examples of System 1 override
in medicine: physicians ignore well-developed clinical decision
rules, even though the rules will consistently outperform them, or
they persist with clinical practices for which there is no
substantive evidence, or otherwise sustain habits that may actually
be counter-therapeutic. In a landmark study in the United States,
barely half of patients were found to be receiving recommended
standards of care (McGlynn et al. 2003).

Thus, we need to appreciate the vulnerability of System 1, that
most errors in decision-making occur here. System 1 is especially
prone to the human tendency to contextualize features of
situations, and there are many ways in which such context adds
meaning to our perceptions and comprehension of events in the world
around us. But on occasions, the situation actually calls for
reasoned and more deliberate decision-making, which may require
some cognitive flexibility in decoupling features that are
irrelevant. It appears that when decisions fail, we have probably
mis-contextualized information or failed to ignore distracting
features.

The Rational-Experiential Inventory

It is not simply the situation or context, however, that
determines whether System 1 or System 2 reasoning will prevail.
Individual proclivities exist, reflecting different ways of looking
at the world (Epstein 1994), presumably based on personality and
other individual differences (Stanovich and West 2002). On the
basis of cognitive-experiential self theory, Epstein and colleagues
have developed the 40-item Rational Experiential Inventory (Pacini
and Epstein 1999), which allows estimates of individuals'
tendencies toward System 1 and System 2 thinking.

Contextual Decision-Making

All decisions are made in some sort of context. It can be
adjacent, as in the perceptual examples in Figures 1-4, or
situational, as in the homicide example, where a variety of
factors, such as previous experience, ambient conditions, current
affective state of the decision-maker, fatigue, sleep deprivation,
expectations etc., are co-determinants. Also, as noted above in the
variety of factors known to influence physicians' decision-making,
context can simply be the visual presentation or some other
characteristic of the patient (e.g., gender, race, obesity,
psychiatric co-morbidity, age). In How Doctors Think,
Montgomery discusses the practical reasoning integral to
physicians' judgment (Montgomery 2006). This requires a hermeneutic
approach - making sense of and interpreting context. Some part of
the context will always be noise and irrelevant to the signal. Not
infrequently, we fail to recognize noise for what it is.

Typically, when we review decisions - our own or those of others
- we cannot reproduce the exact context in which the decisions were
originally made, achieving usually no more than an approximation.
Given that much of our learning occurs in hindsight (i.e., we
accrue wisdom after events), the fallibility of human memory and
the lack of awareness of contextual factors inevitably lead to
imperfect learning. Hindsight is typically (but not necessarily)
subject to bias. Our failure to reconstruct context reliably is a
major impediment to learning.

Hammond (2000), in his seminal work Human Judgment and Social
Policy, emphasized the irreducible uncertainty of
decision-making in several spheres, including medicine and the
judicial system. Both are especially vulnerable when critical
events are judged retrospectively; difficulties are inevitably
encountered in trying to reconstruct the context in which decisions
and actions originally occurred. This is the case for most
evaluations of criminal acts - with the passage of time, failed
memories, unconscious acts and hindsight bias, the past may be
reconstructed as only a pale and blurred image of what it really
was. Judges and juries may sit in dispassionate isolation from
important contextual information that might have strongly
influenced the decisions that were made at the time. Similar
constraints apply to morbidity and mortality conferences and
critical incident reviews. A single case, and the decision-making
that went along with it, is typically separated from the context in
which it occurred. Usually, no account is taken of ambient
conditions, such as other cases being managed concurrently, team
dynamics, fatigue, sleep deprivation and other variables critical
to performance.

Conclusions

The emergence of the dual process model of reasoning has allowed
closer scrutiny of the processes that underlie decision-making and
especially permits a focus on vulnerable aspects of the process.
Despite the fallibility of System 1 reasoning, it is clear that we
cannot live without it. In any event, we could not depend
exclusively on System 2. It requires a major commitment of time and
resources that simply is often not available. Thus, both systems
are essential, performing functions vital to the commerce of daily
living. The key to a well-calibrated performance is some optimal
balance between the two.

However, most errors do occur in System 1, so we need to
understand its vulnerability. It is especially prone to the human
tendency to contextualize features of situations requiring
decision-making. Failed decision-making is due, in part, to an
under- or over-appreciation of contextual cues. Further, when we
are engaged in formal processes that systematically review
decisions that have been made, we need to reconstruct the context
as accurately as possible.

Law and medicine both lean heavily on retrospective processes.
The proper purpose of the legal system is to establish an
understanding of past events such that justice might be fairly
administered. The nature of medicine is significantly dependent on
learning about disease, usually after the fact, so that future
patients might be better diagnosed and treated.

About the Author

Pat Croskerry, MD, PhD, is a professor in the Department of Emergency Medicine, and Division of Medical Education, Faculty of Medicine, Dalhousie University in Halifax, Nova Scotia

Mukherjee, R., A. Fialho, A. Wijetunge, K. Checinski and T. Surgenor. 2002. "The Stigmatisation of Psychiatric Illness: The Attitudes of Medical Students and Doctors in a London Teaching Hospital." Psychiatric Bulletin 26: 178-81.

Pacini, R. and S. Epstein. 1999. "The Relation of Rational and Experiential Information Processing Styles to Personality, Basic Beliefs, and the Ratio-Bias Phenomenon." Journal of Personality and Social Psychology 76: 972-87.